Why a Physics Revolution Might Be on Its Way

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The field of physics may be turned on its head soon, said
renowned physicist Nima Arkani-Hamed during a live lecture from
the Perimeter Institute for Theoretical Physics in Waterloo,
Canada.

For one, he said, the tried and true physics of relativity and
quantum mechanics don't get along well. The problem is that
in some sense, the principles behind these theories seem to be
impossible when physicists dig a little deeper into them,
Arkani-Hamed said. Scientists run into a lot of problems when
they try to apply these theories to the entirety of space and
time.

"It's almost impossible to monkey around with the rules and not
be wrong immediately," Arkani-Hamed said.

Physicists have known about this disparity for a while, but
progress on fundamental questions in physics takes a long time.
Scientists proposed the existence of the
Higgs boson particle, for example, decades before it was
actually discovered.

An unexplained macroscopic universe

One problem is that conventional physics doesn't really account
for why the universe is so large, Arkani-Hamed said.

Albert Einstein's theory
of relativity showed that a huge amount of energy exists in
the vacuum of space, and it should curve space and time. In fact,
there should be so much curvature that the universe is a tiny,
crumpled ball.

"That should make the universe horrendously different than what
it is," Arkani-Hamed said.

But quantum mechanics also poses a problem. The theory is good at
describing the very small realm of
particle physics, but it breaks down when physicists try to
apply it to the universe as a whole.

"Everything that quantum mechanics is, is violated by our
universe because we're accelerating (referring to the idea that
the universe is expanding) – we don't know what the rules are,"
Arkani-Hamed said. "When you try to apply quantum mechanics to
the entire universe, quantum mechanics cries 'uncle.'"

One idea is called string theory, which proposes that particles
aren't actually fundamentally particles. Instead, the particles
and all the matter in the universe they make up are composed of
tiny, vibrating strings. The equations that support string theory
appear to work, but that doesn't mean there are no other viable
formulas or explanations, Arkani-Hamed
said.

Supersymmetry is another possible "new physics"
explanation. Under this idea, all subatomic particles have a
"superpartner" particle that physicists have yet to discover.
Supersymmetry would also open up extra directions that the
particles can move in. The discovery of supersymmetry would
bolster the Standard Model of physics, scientists have said.

"It's the last thing nature can do to make itself compatible with
the general principles of physics that already exist,"
Arkani-Hamed said.

When the world's largest atom smasher,
the Large Hadron Collider (LHC), is up and running again next
year, physicists will be looking for the extra particles that
supersymmetry suggests should exist.

Either way, after a year or two of running the LHC, the question
of whether supersymmetry exists should be answered, Arkani-Hamed
said.

The experiments over the next few years will likely tell
physicists if they need to fine-tune existing theories or if the
field of physics is due for a much deeper and more dramatic
paradigm shift.

The questions on the table now are the underpinnings of space and
time, and the origin and fate of the universe, Arkani-Hamed said.

"Today we finally have the theoretical framework in place to ask
these kinds of big questions," Arkani-Hamed said. "The next step
will likely be a revolution."